It is well known in motor vehicles to provide an air bag module mounted beneath an opening in the instrument panel. The module typically includes a housing having walls defining a housing opening. The module also typically includes an air bag having a mouth portion secured to the housing and including an air bag opening. An inflator is mounted in the housing and discharges inflator gas out the housing opening and into the air bag opening to inflate the air bag when sensing predetermined vehicle conditions. The opening in the instrument panel is typically covered by a hinged cover door which is forced open by the deploying air bag.
It is well known in the prior art to provide a device for verifying that the inflator was sufficiently charged to properly inflate the air bag during deployment. These devices are typically internal to the inflator and detect the pressure level of compressed gases in the inflator, particularly in hybrid inflators. However, these pressure detection devices which are internal to the inflator are relatively expensive and further complicate the design and reliability of the inflator.
It is also known in the prior art to provide pleats either on the air bag or pleats on internal tethers of the air bag which include breakable seams. These pleats and breakable seams are structural components of the air bag which are designed to deter or alter the deployment pattern of the air bag. The breakable seams break at an intermediate deployment time when the air bag is partially inflated to allow the air bag to continue inflating to the fully inflated condition, for example, to control the shape of the bag during deployment. These pleats are typically located on the middle portion of the air bag or near the contact face of the air bag which contacts the occupant during deployment.
The prior art pleats and breakable seams are not designed to detect whether the air bag was properly inflated during air bag deployment since they are designed to break prior to full air bag inflation. In addition, these prior art pleats or breakable seams are structural components of the air bag which control or defer deployment of the air bag and thus do not detect whether proper air bag inflation has occurred. The internal pressure detection devices in an inflator can verify that inflator gas was sufficient for proper air bag inflation, but are expensive and complicated to provide.